Whitman was born in Oak Park, Tampa, Florida, on January 20, 1923,[5][6][7] one of six siblings[citation needed], to Ottis Dewey Whitman Sr. (1896-1961) and Lucy Whitman (née Mahon) (1903–1987).
Whitman was married to Alma Geraldine "Jerry" Crist Whitman for 67 years. Jerry was born in Kansas, the daughter of church minister, A.D. Crist. She was an songwriter and embroider. Together Whitman and his wife had a daughter, Sharron Beagle (b. 1942), and a son, Byron Keith Whitman (b. 1957). They also had two grandchildren and two great-grandchildren.[12]
After 1957 Whitman lived at his estate, Woodpecker Paradise, in Middleburg, a city located south of Orange Park, Florida, in Clay County.
Slim Whitman died of heart failure on June 19, 2013, at age 90, surrounded by family at Orange Park Medical Center in Orange Park, Florida. He is buried in the Middleburg Methodist Church Cemetery, Middleburg, Florida.